I've never seen placement of the bullets of a list in the margin. The text within a list isn't just body text. So, why line it up with body text. It's a good idea to indent it like you would do with a quotation.
Let's think of choosing this style. What about a nested list? In consequence, its items would have to be aligned at the left margin of the parent list, so at the left margin of the document as well.
What about enumerated lists? Should the numbers be placed in the margin?
To sum up, bulleted list with bullets in margins and items in line with body text seems questionable. Though, it can easily be achieved.
With enumitem, better specify a style in the preamble than to each list by an optional argument. This is consistent and allows easy changes. If you later decide to change the list style, you just need to apply the modification once in the preamble for the whole document.
Martin's example modified under this point of view: